Materials and methods for producing alkenes and derivatives thereof

ABSTRACT

The present disclosure relates to processes for production of alkene products from their alkene precursors, such as 3-hydroxyacid and alcohols, via either (1) high temperature reactive distillation with steam contact at optimal pH, (2) solvent extraction and Mulzer dehydration, (3) solid phase adsorption, desorption into an organic solvent and catalytic reaction and (4) high temperature reactive distillation with steam contact at optimal pH followed by catalytic conversion.

TECHNICAL FIELD

The present disclosure relates to for example methods producing alkeneproducts. The present disclosure relates to materials and methodsproducing alkene products from 3-hydroxyacid, and alcohol precursorssynthesized in fermentation, producing such alkenes in down-streamprocessing unit operations. For instance, the methods may be used toproduce one or more of isoprene, butadiene and isobutene from alkeneprecursors. Alkene precursors may be converted to their respectivealkenes via dehydrative decarboxylation or dehydration. Such vinyl groupforming mechanisms may be promoted using, for example, (1) hightemperature reactive distillation with steam contact at optimal pH, (2)solvent extraction followed by Mulzer dehydration, (3) solid phaseadsorption and desorption into a solvent followed by catalyticconversion and (4) high temperature reactive distillation with steamcontact at optimal pH followed by catalytic conversion. Given a relianceon petrochemical feedstocks, biotechnology offers an alternativeapproach to producing alkene precursors to isoprene, butadiene andisobutene.

BACKGROUND

Isoprene is an important monomer for the production of specialtyelastomers including motor mounts/fittings, surgical gloves, rubberbands, golf balls and shoes. Styrene-isoprene-styrene block copolymersform a key component of hot-melt pressure-sensitive adhesiveformulations and cis-poly-isoprene is utilised in the manufacture oftires (Whited et al., Industrial Biotechnology, 2010, 6(3), 152-163).Manufacturers of rubber goods depend on either imported natural rubberfrom the Brazilian rubber tree or petroleum-based synthetic rubberpolymers (Whited et al., Industrial Biotechnology, 2010, 6(3), 152-163).

1,3-Butadiene (referred to herein as “butadiene”) is an importantmonomer for the production of synthetic rubbers includingstyrene-butadiene-rubber (SBR), polybutadiene (PB), styrene-butadienelatex (SBL), acrylonitrile-butadiene-styrene resins (ABS), nitrilerubber, and adiponitrile. Adiponitrile is used in the manufacture ofNylon-6,6 (White, Chemico-Biological Interactions, 2007, 166, 10-14).Butadiene is typically produced as a co-product from the steam crackingprocess, distilled to a crude butadiene stream, and purified viaextractive distillation (White, Chemico-Biological Interactions, 2007,166, 10-14). On-purpose butadiene has been prepared among other methodsby dehydrogenation of n-butane and n-butene (Houdry process); andoxidative dehydrogenation of n-butene (Oxo-D or O-X-D process) (White,Chemico-Biological Interactions, 2007, 166, 10-14). Industrially, 95% ofglobal butadiene production is undertaken via the steam cracking processusing petrochemical-based feedstocks such as naphtha. Production ofon-purpose butadiene is not significant, given the high cost ofproduction and low process yield (White, Chemico-BiologicalInteractions, 2007, 166, 10-14).

Isobutene is an important monomer in the manufacture of fuel additives,butyl rubber polymer, and antioxidants (Bianca et al., Appl. MicrobiolBiotechnol., 2012, 93, 1377-1387). Manufacturers of goods usingisobutene as feedstock depend on a number of petroleum-based sources,including (i) a C4 stream from a steam cracker separated from thebutadiene, (ii) butene-butane fractions from a catalytic cracker and(iii) n-butane (from LPG) that is isomerized to isobutane anddehydrogenated to isobutene (Bianca et al., Appl. Microbiol Biotechnol.,2012, 93, 1377-1387).

Given a reliance on petrochemical feedstocks, biotechnology offers analternative approach to producing alkene precursors to isoprene,butadiene and isobutene. Biocatalysis is the use of biologicalcatalysts, such as enzymes or whole cells, to perform biochemicaltransformations of organic compounds.

Accordingly, against this background, it is clear that there is a needfor sustainable methods for producing precursors to commodity alkenes,in particular isoprene, isobutene and butadiene, wherein the precursorsare biocatalysis based.

SUMMARY

The present disclosure relates to the production of alkene products orderivatives thereof. The present disclosure relates to the production ofalkene products from alkene precursors, such as 3-hydroxyacids andalcohols, derived from fermentation via dehydrative decarboxylation anddehydration respectively.

Accordingly, methods of converting alkene precursors are disclosed,wherein the alkene precursors are derived from fermentation, indownstream processing unit operations to their respective alkenes.

In one aspect, the present disclosure relates to methods comprising (1)high temperature reactive distillation with steam contact of the alkeneprecursor from the clarified fermentation broth, forming the alkeneproduct in situ.

In another aspect, the disclosure relates to (1) solvent extraction ofthe alkene precursor from the clarified fermentation broth, followed by(2) a Mulzer dehydration reaction of the alkene precursor forming therespective alkene.

In another aspect, the present disclosure relates to (1) solid phaseadsorption of the alkene precursor from the clarified fermentation brothand subsequent desorption into an organic solvent, followed by (2)catalytic reaction of the alkene precursor forming the respectivealkene.

In another aspect, the present disclosure relates to (1) distillation orreactive distillation of the alkene precursor from the clarifiedfermentation broth, followed by (2) catalytic reaction of the alkeneprecursor forming the respective alkene.

The present disclosure further relates to methods for recovering thealkene product from one of the three methods described above, furthersubjecting the alkene product to membrane separation, adsorption ordistillation or combinations thereof.

The present disclosure further relates to methods for recovering thealkene product from one of the three methods described above and furthersubjecting the alkene product to an optional polishing distillationstep.

The present disclosure further relates to methods for recovering thealkene product from one of the three methods described above and furthersubjecting the alkene product to a condensation step.

The present disclosure further relates to a bio-derived product,bio-based product or fermentation-derived product, wherein said productis obtained from the process disclosed herein, and comprises:

-   -   i. a composition comprising at least one bio-derived, bio-based        or fermentation-derived compound according to any process        disclosed herein, or any one of FIGS. 1-9, or any combination        thereof,    -   ii. a bio-derived, bio-based or fermentation-derived polymer        comprising the bio-derived, bio-based or fermentation-derived        composition or compound of i., or any combination thereof,    -   iii. a bio-derived, bio-based or fermentation-derived resin        comprising the bio-derived, bio-based or fermentation-derived        compound or bio-derived, bio-based or fermentation-derived        composition of i. or any combination thereof, or the        bio-derived, bio-based or fermentation-derived polymer of ii. or        any combination thereof,    -   iv. a molded substance obtained by molding the bio-derived,        bio-based or fermentation-derived polymer of ii. or the        bio-derived, bio-based or fermentation-derived resin of iii., or        any combination thereof,    -   v. a bio-derived, bio-based or fermentation-derived formulation        comprising the bio-derived, bio-based or fermentation-derived        composition of i., bio-derived, bio-based or        fermentation-derived compound of i., bio-derived, bio-based or        fermentation-derived polymer of ii., bio-derived, bio-based or        fermentation-derived resin of iii., or bio-derived, bio-based or        fermentation-derived molded substance of iv, or any combination        thereof, or    -   vi. a bio-derived, bio-based or fermentation-derived semi-solid        or a non-semi-solid stream, comprising the bio-derived,        bio-based or fermentation-derived composition of i.,        bio-derived, bio-based or fermentation-derived compound of i.,        bio-derived, bio-based or fermentation-derived polymer of ii.,        bio-derived, bio-based or fermentation-derived resin of iii.,        bio-derived, bio-based or fermentation-derived formulation of        v., or bio-derived, bio-based or fermentation-derived molded        substance of iv., or any combination thereof.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this present disclosure pertains. Although methods andmaterials similar or equivalent to those described herein can be used topractice the present disclosure, suitable methods and materials aredescribed below. All publications, patent applications, patents, andother references mentioned herein are incorporated by reference in theirentirety. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

The details of one or more embodiments of the present disclosure are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the present disclosure will beapparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of an exemplary process flow diagram comprisinghigh temperature reactive distillation with steam contact, converting analkene precursor derived from fermentation to the respective alkeneproduct.

FIG. 2 is a schematic of an exemplary process flow diagram comprisingsolvent extraction and Mulzer dehydration, converting an alkeneprecursor derived from fermentation to the respective alkene product.

FIG. 3 is a schematic of an exemplary process flow diagram comprisingadsorption of the alkene precursor from the clarified fermentationbroth, followed by desorption into an organic solvent and thereafterconverted via catalytic reaction to the respective alkene.

FIG. 4 is a schematic of an exemplary process flow diagram comprisinghigh temperature reactive distillation with steam contact of the alkeneprecursor, followed by catalytic conversion to the respective alkeneproduct.

FIG. 5 tabulates the conversion of alkene precursors to alkene productsat elevated temperature and acidic pH in DSMZ media 81 as analyzed viaGC-MS.

FIG. 6 graphs the continuous conversion of3-hydroxy-3-methylpent-4-enoic acid to isoprene at elevated temperatureand acidic pH in DSMZ media 81 in a reactive distillation unit operationwith steam contact, showing the approach to steady state conversionalongside feed rate and total vapor product flow rate.

FIG. 7 graphs the continuous conversion of3-hydroxy-3-methylpent-4-enoic acid to isoprene at elevated temperatureand acidic pH in DSMZ media 81 in a reactive distillation unit operationwith steam contact, showing the approach to steady state conversionalongside reboiler temperature.

FIG. 8 graphs the continuous conversion of 3-hydroxy-3-methylbutyricacid to isobutene at elevated temperature and acidic pH in DSMZ media 81in a reactive distillation unit operation with steam contact, showingthe approach to steady state conversion alongside feed rate and totalvapour product flow rate.

FIG. 9 graphs the continuous conversion of 3-hydroxy-3-methylbutyricacid to isobutene at elevated temperature and acidic pH in DSMZ media 81in a reactive distillation unit operation with steam contact, showingthe approach to steady state conversion alongside reboiler temperature.

DETAILED DESCRIPTION

Before the present embodiments are described, it is to be understoodthat the present disclosure is not limited to the particular apparatus,adsorbents, methodologies or protocols described, as these may vary. Itis also to be understood that the terminology used in the description isfor the purpose of describing the particular versions or embodimentsonly, and is not intended to limit the scope of the present disclosure.

In accordance with the present disclosure, the materials and methodsherein relate to the conversion of alkene precursors derived fromfermentation to their respective alkene products. Alkene precursorsinclude, but are not limited to; 3-hydroxyacids such as mevalonate,3-methyl-3-hydroxybutyrate, 3-hydroxypent-4-enoate,3-methyl-3-hydroxypent-4-enoate and 4-methyl-3-hydroxypent-1-enoate;primary alcohols such as 3-methyl-2-buten-1-ol and3-methyl-3-buten-1-ol; secondary alcohols such as 3-buten-2-ol and3-methyl-3-buten-2-ol; tertiary alcohols such as 2-methyl-3-buten-2-ol;all of which are referred to as alkene precursors herein. Alkeneproducts include, but are not limited to, isoprene, butadiene orisobutene. The term “Mulzer dehydration” denotes herein, but is notlimited to, reaction of a dehydrating agent, such as, for example,dimethyl-formamide-dimethylacetal, with an alkene precursor in anorganic solvent, for example, a long chain ester such as hexyl acetateor octanyl acetate. The term “about” or “approximately” when used inconnection with a specific value, means that acceptable deviations fromthat value are also encompassed but still provide substantially the samefunction as the specific value.

High Temperature Reactive Distillation with Steam Contact

Fermentation broth (see e.g., STREAM 1, FIG. 1) can be clarified by, forexample, microfiltration or centrifugal separation or combinationthereof. The separated biomass can be returned to fermentation (seee.g., STREAM 2, FIG. 1) or bled to waste treatment (see e.g., STREAM 4,FIG. 1) or combination thereof.

The clarified fermentation broth originating from microfiltration (seee.g., STREAM 3, FIG. 1) and/or centrifugation (see e.g., STREAM 5,FIG. 1) can be fed to a high temperature reactive distillation unit withsteam contact via a condenser with bypass (see e.g., STREAM 6, FIG. 1)and/or a recovery heat exchanger (see e.g., STREAM 7, FIG. 1). For3-hydroxyacid alkene precursors, the pH of the clarified broth can beadjusted to approximately 3 using an acidic media comprisingconcentrated fermentation media pH adjusted with sulphuric acid orphosphoric acid (see e.g., STREAM 3, FIG. 1). An alkene polymerisationinhibitor can also be added to the feed.

The preheated clarified fermentation broth can be fed to a packed column(see e.g., STREAM 8, FIG. 1) operated at approximately 150° C. bycontacting the feed directly with high pressure steam or indirectly withhigh pressure steam via a reboiler.

The column bottoms hold-up can be recycled (see e.g., STREAM 11, FIG. 1)to the feed position, whilst bottoms withdrawal (see e.g., STREAM 10,FIG. 1) is via a recovery heat exchanger. The feed rate to the reactivedistillation unit (see e.g., STREAM 8, FIG. 1) is controlled to minimisethe concentration of at least one alkene precursor in the bottomsoutflow (see e.g., STREAM 12, FIG. 1).

The high temperature reactive distillation with steam contact increasesthe reaction rate for the dehydrative decarboxylation of 3-hydroxyacids,such as mevalonate, 3-methyl-3-hydroxybutyrate, 3-hydroxypent-4-enoate,3-methyl-3-hydroxypent-4-enoate and 4-methyl-3-hydroxypent-4-enoate andthe dehydration of such as 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol,3-buten-2-ol, 3-methyl-3-buten-2-ol and 2-methyl-3-buten-2-ol to theirrespective alkene products.

The alkene product mixture is withdrawn as top product from the reactivedistillation unit (see e.g., STREAM 9, FIG. 1) and the top product canbe partially condensed, retaining the alkene product mixture in thevapour phase (see e.g., STREAM 13, FIG. 1).

The condensed fraction of the top product can be returned to thecolumn's feed position (see e.g., STREAM 14, FIG. 1), recycling, forexample, unreacted alkene precursors such as azeotropic alcohols to thereactive distillation unit. The top product recycle (see e.g., STREAM14, FIG. 1) flow rate maintains a low concentration of unreacted alkeneprecursors in the top product outflow (see e.g., STREAM 15, FIG. 1).

The water saturated alkene product mixture (see e.g., STREAM 16, FIG. 1)can be fed to a drying unit operation, packed with an adsorbent such asa molecular sieve, removing water (see e.g., STREAM 17, FIG. 1) to a lowdew point of, for example, −20° C. and produce a dry alkene productmixture.

The dry alkene product mixture (see e.g., STREAM 18, FIG. 1) can be fedto an adsorption unit operation packed with an adsorbent selective foralkenes such as a zeolite. Volatile organic by-products, such asalcohols and aldehydes, originating from the clarified fermentationbroth are removed in the adsorption flow-through (see e.g., STREAM 23,FIG. 1), whilst the alkene product is desorbed using, for example,nitrogen to produce a desorbed alkene product (see e.g., STEAM 25, FIG.1). The desorbed alkene product can be fed to a polishing distillationunit operation optionally involving a pre-condenser via compression orchilling(see e.g., STREAM 26, FIG. 1), followed by a condensation unitoperation producing the high purity alkene product (see e.g., STREAM 29,FIG. 1). The desorbed alkene product can also be fed directly to acondensation unit operation (see e.g., STREAM 27, FIG. 1), producing thehigh purity alkene product (see e.g., STREAM 29, FIG. 1). Separation ofthe alkene from any permanent gases, such as nitrogen, can be achievedby, for example, complete condensation of the desorbed alkene product.

The dry alkene product (see e.g., STREAM 18, FIG. 1) can be fed to amembrane separation unit operation using a membrane selective foralkenes such as a zeolite membrane. Volatile organic by-products, suchas alcohols and aldehydes, originating from the clarified fermentationbroth are removed via the retentate bleed (see e.g., STREAM 22, FIG. 1),whilst the alkene product is collected as permeate (see e.g., STREAM 24,FIG. 1). The permeate containing the alkene product can be fed to apolishing distillation unit operation optionally involving apre-condenser via compression or chilling (see e.g., STREAM 26, FIG. 1)to remove impurities (see e.g., STREAM 28, FIG. 1), followed by acondensation unit operation producing the high purity alkene product(see e.g., STREAM 29, FIG. 1). The permeate containing the alkeneproduct can also be fed directly to a condensation unit operation (seee.g., STREAM 27, FIG. 1), producing the high purity alkene product (seee.g., STREAM 29, FIG. 1).

The dry alkene product (see e.g., STREAM 18, FIG. 1) can be fed directlyto a distillation unit operation (see e.g., STREAM 21, FIG. 1), followedby a condensation unit operation producing the high purity alkeneproduct (see e.g., STREAM 29, FIG. 1).

Solvent Extraction and Mulzer Dehydration Reaction

Fermentation broth (see e.g., STREAM 1, FIG. 2) can be clarified by, forexample, microfiltration or centrifugal separation or combinationthereof. The separated biomass can be returned to fermentation (seee.g., STREAM 2, FIG. 2) or bled to waste treatment (see e.g., STREAM 4,FIG. 2) or a combination thereof. The clarified fermentation brothoriginating from microfiltration (see e.g., STREAM 3, FIG. 2) and/orcentrifugation (see e.g., STREAM 5, FIG. 2) can be fed to a solventextraction unit operation (see e.g., STREAM 6, FIG. 2), contacting asolvent that has a high selectively for 3-hydroxyacids or alcohols, lowmiscibility in water and promotes Mulzer dehydration reactions, forexample, a long chain ester such as hexyl acetate or octanyl acetate; toproduce a solvent extracted alkene precursor (see e.g., STREAM 7, FIG.2). In one aspect, the clarified fermentation broth is extracted with asolvent comprising a long chain ester such as hexyl acetate and octanylacetate.

The solvent extracted alkene precursor mixture is fed (see e.g., STREAM7, FIG. 2) to a dehydration reactor, contacting the solvent extractedalkene precursor with a Mulzer dehydrating agent such asdimethyl-formamide-dimethylacetal, forming an alkene product mixture.The dehydrating reactor's solvent phase can be fed to a distillationtrain (see e.g., STREAM 8, FIG. 2), recycling the solvent to the solventextraction unit operation (see e.g., STREAM 9, FIG. 2) and feeding theMulzer dehydrating agent to a regeneration reactor (see e.g., STREAM 10,FIG. 2). The regenerated Mulzer dehydrating agent can be recycled to thedehydrating reactor (see e.g., STREAM 11, FIG. 2).

The alkene product mixture in the vapour phase of the dehydratingreactor (see e.g., STREAM 12, FIG. 2) can be fed (see e.g., STREAM 14,FIG. 2) to an adsorption unit operation packed with an adsorbentselective for alkenes such as a zeolite. Volatile organic by-products,such as alcohols and aldehydes, originating from the clarifiedfermentation broth are removed in the adsorption flow-through (see e.g.,STREAM 17, FIG. 2), whilst the alkene product is adsorbed andsubsequently desorbed using, for example, nitrogen to produce a desorbedalkene product (see e.g., STEAM 19, FIG. 2). The desorbed alkene productcan be fed to a polishing distillation unit operation optionallyinvolving a pre-condenser via compression or chilling (see e.g., STREAM20, FIG. 2) to remove impurities (see e.g., STREAM 22, FIG. 2), followedby a condensation unit operation producing the high purity alkeneproduct (see e.g., STREAM 23, FIG. 2). The desorbed alkene product canalso be fed directly to a condensation unit operation (see e.g., STREAM21, FIG. 2), producing the high purity alkene product (see e.g., STREAM23, FIG. 2).

The alkene product mixture in the vapour phase of the dehydratingreactor (see e.g., STREAM 12, FIG. 2) can be fed (see e.g., STREAM 13,FIG. 2) to a membrane separation unit operation using a membraneselective for alkenes such as a zeolite membrane. Volatile organicby-products, such as alcohols and aldehydes, originating from theclarified fermentation broth are removed via the retentate bleed (seee.g., STREAM 16, FIG. 2), whilst the alkene product is collected aspermeate (see e.g., STREAM 18, FIG. 2). The permeate containing thealkene product can be fed to a polishing distillation unit operationoptionally involving a pre-condenser via compression or chilling (seee.g., STREAM 20, FIG. 2), followed by a condensation unit operationproducing the high purity alkene product (see e.g., STREAM 23, FIG. 2).The permeate containing the alkene product can also be fed directly to acondensation unit operation (see e.g., STREAM 21, FIG. 2), producing thehigh purity alkene product (see e.g., STREAM 23, FIG. 2).

Solid Phase Adsorption, Desorption into Organic Solvent and CatalyticReaction

Fermentation broth (see e.g., STREAM 1, FIG. 3) can be clarified by, forexample, microfiltration or centrifugal separation or combinationthereof. The separated biomass can be returned to fermentation (seee.g., STREAM 2, FIG. 3) or bled to waste treatment (see e.g., STREAM 4,FIG. 3) or combination thereof. The clarified fermentation brothoriginating from microfiltration (see e.g., STREAM 3, FIG. 3) and/orcentrifugation (see e.g., STREAM 5, FIG. 3) can be fed to an adsorptionunit operation (see e.g., STREAM 6, FIG. 3), contacting a solid phaseadsorbent that has high selectively for 3-hydroxyacids, such as ananionic exchange resin, or alcohols, such as a weakly polar polystyrenemacroporous resin or a zeolite. The adsorbed precursor is desorbed into(1) high concentration aqueous ammonia or ammonium (bi)carbonate or (2)an organic solvent such as methanol.

The desorbed alkene precursor is fed (see e.g., STREAM 7, FIG. 3) to adistillation step, comprising one or more distillation units, purifyingthe desorbed alkene precursor as a suitable feed to a catalytic reactor(see e.g., STREAM 9, FIG. 3). The desorbent recovered duringdistillation can be recycled to the adsorption unit operation (see e.g.,STREAM 8, FIG. 3).

The catalytic reactor converts the at least one alkene precursor (seee.g., STREAM 9, FIG. 3) to the alkene product mixture using (1) adehydrating or dehydrative decarboxylating catalyst such as thoriumoxide at high temperature or (2) high temperature in the absence of acatalyst. Unreacted alkene precursor can be recycled to the catalyticreactor feed (see e.g., STREAM 10, FIG. 3).

The alkene product mixture in the vapour phase of the catalytic reactorcan be fed (see e.g., STREAM 12, FIG. 3) to an adsorption unit operationpacked with an adsorbent selective for alkenes such as a zeolite.Volatile organic by-products are removed in the adsorption flow-through(see e.g., STREAM 15, FIG. 3), whilst the alkene product is adsorbed andsubsequently desorbed using, for example, nitrogen to produce a desorbedalkene product (see e.g., STEAM 17, FIG. 3). The desorbed alkene productcan be fed to a polishing distillation unit operation optionallyinvolving a pre-condenser via compression or chilling (see e.g., STREAM18, FIG. 3) to remove impurities (see e.g., STREAM 20, FIG. 3), followedby a condensation unit operation producing the high purity alkeneproduct (see e.g., STREAM 21, FIG. 3). The desorbed alkene product canalso be fed directly to a condensation unit operation (see e.g., STREAM19, FIG. 3), producing the high purity alkene product (see e.g., STREAM21, FIG. 3).

The alkene product mixture in the vapour phase of the catalytic reactorcan be fed (see e.g., STREAM 11, FIG. 3) to a membrane separation unitoperation using a membrane selective for alkenes such as a zeolitemembrane. Volatile organic by-products can be removed via the retentatebleed (see e.g., STREAM 14, FIG. 3), whilst the alkene product iscollected as permeate (see e.g., STREAM 16, FIG. 3). The permeatecontaining the alkene product can be fed to a polishing distillationunit operation optionally involving a pre-condenser via compression orchilling (see e.g., STREAM 18, FIG. 3) to remove impurities (see e.g.,STREAM 20, FIG. 3), followed by a condensation unit operation producingthe high purity alkene product (see e.g., STREAM 21, FIG. 3). Thepermeate containing the alkene product (see e.g., STREAM 16, FIG. 3) canalso be fed directly to a condensation unit operation (see e.g., STREAM19, FIG. 3), producing the high purity alkene product (see e.g., STREAM21, FIG. 3).

High Temperature Reactive Distillation with Steam Contact and CatalyticReaction

Fermentation broth (see e.g., STREAM 1, FIG. 4) can be clarified by, forexample, microfiltration or centrifugal separation or combinationthereof. The separated biomass can be returned to fermentation (seee.g., STREAM 2, FIG. 4) or bled to waste treatment (see e.g., STREAM 4,FIG. 4) or combination thereof.

The clarified fermentation broth originating from microfiltration (seee.g., STREAM 3, FIG. 4) and/or centrifugation (see e.g., STREAM 5, FIG.4) can be fed to a high temperature reactive distillation unit withsteam contact via a condenser with bypass (see e.g., STREAM 6, FIG. 4)and/or a recovery heat exchanger (see e.g., STREAM 7, FIG. 4). For3-hydroxyacid alkene precursors, the pH of the clarified broth can beadjusted to approximately 3 using an acidic media comprisingconcentrated fermentation media pH adjusted with sulphuric acid orphosphoric acid (see e.g., STREAM 3, FIG. 4). An alkene polymerisationinhibitor can also be added to the feed.

The preheated clarified fermentation broth can be fed to a packed column(see e.g., STREAM 8, FIG. 4) operated at approximately 150° C. bycontacting the feed directly with high pressure steam or indirectly withhigh pressure steam via a reboiler.

The column bottoms hold-up can be recycled (see e.g., STREAM 11, FIG. 4)to the feed position, whilst bottoms withdrawal (see e.g., STREAM 10,FIG. 4) is via a recovery heat exchanger. The feed rate to the reactivedistillation unit (see e.g., STREAM 8, FIG. 4) is controlled to minimisethe concentration of at least one alkene precursor in the bottomsoutflow (see e.g., STREAM 12, FIG. 4).

The high temperature reactive distillation with steam contact increasesthe reaction rate for the dehydrative decarboxylation of 3-hydroxyacids,such as mevalonate forming either 3-methyl-2-buten-1-ol and/or3-methyl-3-buten-1-ol. The high temperature distillation recoversazeotropic alcohols such as 3-methyl-2-buten-1-ol,3-methyl-3-buten-1-ol, 3-buten-2-ol, 3-methyl-3-buten-2-ol and2-methyl-3-buten-2-ol to the distillate product (see e.g., STREAM 9,FIG. 4).

The alkene/alcohol product mixture is withdrawn as top product from thereactive distillation unit (see e.g., STREAM 9, FIG. 4) and the topproduct can be partially condensed, retaining the alkene product mixturein the vapour phase (see e.g., STREAM 13, FIG. 4).

The condensed fraction of the top product can be returned to thecolumn's feed position (see e.g., STREAM 14, FIG. 4), recycling, forexample, unreacted alkene precursors such as azeotropic alcohols to thereactive distillation unit. The top product recycle (see e.g., STREAM14, FIG. 4) flow rate maintains an azeotropic concentration of unreactedalkene precursors in the top product outflow (see e.g., STREAM 15, FIG.4). The azeotropic concentration of unreacted alkene precursors (seee.g., STREAM 15, FIG. 4) can be fed to a catalytic reactor. Thecatalytic reactor converts the at least one alkene precursor (see e.g.,STREAM 15, FIG. 4) to the alkene product mixture using (1) a dehydratingcatalyst such as thorium oxide at high temperature or (2) hightemperature in the absence of a catalyst. Unreacted alkene precursor canbe recycled to the catalytic reactor feed (see e.g., STREAM 17, FIG. 4).

The water saturated alkene product mixture (see e.g., STREAM 16, FIG. 4)and the catalytic reactor product (see e.g., STREAM 18, FIG. 4) can befed to a drying unit operation, packed with an adsorbent such as amolecular sieve, removing water (see e.g., STREAM 19, FIG. 4) to a lowdew point of, for example, −20° C. and produce a dry alkene productmixture.

The dry alkene product mixture (see e.g., STREAM 21, FIG. 4) can be fedto an adsorption unit operation packed with an adsorbent selective foralkenes such as a zeolite. Volatile organic by-products, such asalcohols and aldehydes, originating from the clarified fermentationbroth are removed in the adsorption flow-through (see e.g., STREAM 24,FIG. 4), whilst the alkene product is desorbed using, for example,nitrogen to produce a desorbed alkene product (see e.g., STEAM 25, FIG.4). The desorbed alkene product can be fed to a polishing distillationunit operation optionally involving a pre-condenser via compression orchilling (see e.g., STREAM 25, FIG. 4), followed by a condensation unitoperation producing the high purity alkene product (see e.g., STREAM 30,FIG. 4). The desorbed alkene product can also be fed directly to acondensation unit operation (see e.g., STREAM 28, FIG. 4), producing thehigh purity alkene product (see e.g., STREAM 30, FIG. 4). Separation ofthe alkene from any permanent gases, such as nitrogen, can be achievedby, for example, complete condensation of the desorbed alkene product.

The dry alkene product (see e.g., STREAM 20, FIG. 4) can be fed to amembrane separation unit operation using a membrane selective foralkenes such as a zeolite membrane. Volatile organic by-products, suchas alcohols and aldehydes, originating from the clarified fermentationbroth are removed via the retentate bleed (see e.g., STREAM 23, FIG. 4),whilst the alkene product is collected as permeate (see e.g., STREAM 26,FIG. 4). The permeate containing the alkene product can be fed to apolishing distillation unit operation optionally involving apre-condenser via compression or chilling (see e.g., STREAM 26, FIG. 4)to remove impurities (see e.g., STREAM 27, FIG. 4), followed by acondensation unit operation producing the high purity alkene product(see e.g., STREAM 30, FIG. 4). The permeate containing the alkeneproduct can also be fed directly to a condensation unit operation (seee.g., STREAM 28, FIG. 4), producing the high purity alkene product (seee.g., STREAM 30, FIG. 4).

The dry alkene product can be fed directly to a distillation unitoperation (see e.g., STREAM 22, FIG. 4), followed by a condensation unitoperation producing the high purity alkene product (see e.g., STREAM 30,FIG. 4).

EXAMPLES Example 1 Conversion of Alkene Precursors Dissolved inFermentation Media to Alkene Products Via Residence Time at ElevatedTemperature at Optimal pH

DSMZ fermentation medium 81 was adjusted to pH=3.0 using concentratedphosphoric acid. The acidic fermentation medium was pipetted into GCvials and preheated to 95 [° C.]. Each of the alkene precursorstabulated in FIG. 5 was pipetted into the GC vials individually induplicate to either a final concentration of 500 [ppm] or 1000 [ppm] asoutlined in FIG. 5. Each GC vial was immediately crimped and incubatedat 95 [° C.] for 30 [min]. The vials were cooled to room temperatureprior to GC-MS analysis.

For isoprene analysis via GC-MS, a standard curve was generated using anisoprene in methanol analytical standard dispensed into the acidicfermentation media, measuring the isoprene concentration in theheadspace of the vials. Isobutene formation was confirmed via ananalytical standard prepared by saturating isobutene gas in water,measuring the isobutene concentration in the headspace of the standard.

FIG. 5 outlines the conversion of each alkene precursor to itsrespective alkene product. The alkene precursors3-hydroxy-3-methylpent-4-enoic acid and 3-hydroxy-3-methylbutyric acidwere converted to isoprene and isobutene respectively at highconversion. The conversion of 3-hydroxy-4-methylpent-4-enoic acid wasdetected.

The alkene precursors 3-methyl-2-buten-1-ol and 2-methyl-3-buten-2-olwere converted to isoprene at moderate conversion, whilst conversion of3-methyl-3-buten-1-ol to isoprene was detected.

Mevalonic acid conversion to isoprene in DSMZ-81 fermentation media atpH ≤3.0 was detected alongside a peak predicted by GC-MS to be either3-methyl-3-buten-1-ol or 3-methyl-2-buten-1-ol.

The results presented in FIG. 5 demonstrate that 3-hydroxyacids alkeneprecursors, such as 3-hydroxy-3-methylpent-4-enoic acid,3-hydroxy-3-methylbutyric acid, 3-hydroxy-4-methylpent-4-enoic acid andmevalonic acid, can be converted in DSMZ-81 fermentation media to theirrespective alkene products at elevated temperature and acidic pH.

The results presented in FIG. 5 demonstrate that alcohol precursors toalkene products, such as 3-methyl-2-buten-1-ol, 2-methyl-3-buten-2-oland 3-methyl-3-buten-1-ol, can be converted in DSMZ-81 fermentationmedia to their respective alkene products at elevated temperature andacidic pH.

The results presented in FIG. 5 demonstrate that mevalonic acid can beconverted in DSMZ-81 fermentation media to isoprene and3-methyl-3-buten-1-ol/3-methyl-2-buten-1-ol (predicted) respectively atelevated temperature and acidic pH.

Example 2 Conversion of 3-Hydroxy-3-Methylpent-4-Enoic Acid Dissolved inFermentation Media to Isoprene Via Reactive Distillation with SteamContact at Optimal pH

A large scale laboratory reactive distillation unit with a temperaturecontrolled flash drum was designed to operate at elevated pressure andtemperature to demonstrate the continuous conversion of 3-hydroxyacidprecursors to their respective alkene products. The flash drum wasfitted with a knock-out after-cooler fed with chilled water atapproximately 10 [° C.]. The flash drum was charged with water andtemperature controlled to 20 [° C.]. The vapour product from thedistillation unit was bubbled through the water charge and a constantflow of N₂ at 0.3 [SL/min] was introduced as carrier and stripping gas.The uncondensed vapour product from the flash drum was fed to a RamanSpectrometer, calibrated with a 0.5 [%] (v/v) 1,3-butadiene calibrationcylinder as double bond reference gas to analyse for the concentrationof double bonds in the vapour product from the flash drum.

DSMZ fermentation medium 81 was prepared with a five times concentratedtrace metal solution and adjusted to pH=3.0 using phosphoric acid. Thealkene precursor 3-hydroxy-3-methyl-pent-4-enoic acid was dissolved inthe prepared fermentation media to a concentration of 9.5 [(g alkeneprecursor)/(kg total media)]. The reactive distillation unit waspreheated to >120 [° C.] via pressure control. The media containing thealkene precursor was fed to the reactive distillation unit operationinitially at 275 [g/h] to flush the recovery heat exchanger andestablish media holdup in the reboiler (FIG. 6). The reboilertemperature was controlled at 139 [° C.] (FIG. 7) and the feed rate wasdecreased to approximately 160 [g/h], allowing the approach to steadystate operation. The double bond concentration in the vapour productfrom the flash drum was analysed continuously for a period ofapproximately 2.5 [h] (FIG. 6 and FIG. 7), confirming the production ofisoprene to high conversion as anticipated by Example 1. The resultspresented in FIG. 6 and FIG. 7 demonstrate that3-hydroxy-3-methylpent-4-enoic acid can be converted in concentratedDSMZ-81 fermentation media to isoprene in a reactive distillation unitwith steam contact at elevated temperature and acidic pH.

Example 3 Conversion of 3-Hydroxy-3-Methylbutyric Acid Dissolved inFermentation Media to Isobutene Via Reactive Distillation with SteamContact at Optimal pH

A large scale laboratory reactive distillation unit with a temperaturecontrolled flash drum was designed to operate at elevated pressure andtemperature to demonstrate the continuous conversion of 3-hydroxyacidprecursors to their respective alkene products. The flash drum wasfitted with a knock-out after-cooler fed with chilled water atapproximately 8 [° C.]. The flash drum was charged with water andtemperature controlled to 10 [° C.]. The vapour product from thedistillation unit was bubbled through the water charge and a constantflow of N₂ at 0.3 [SL/min] was introduced as carrier and stripping gas.The uncondensed vapour product from the flash drum was fed to a RamanSpectrometer, calibrated with a 0.5 [%] (v/v) 1,3-butadiene calibrationcylinder as double bond reference gas to analyse for the concentrationof double bonds in the vapour product from the flash drum.

DSMZ fermentation medium 81 was prepared with a five times concentratedtrace metal solution and adjusted to pH=3.0 using phosphoric acid. Thealkene precursor 3-hydroxy-3-methyl-butyric acid was dissolved in theprepared fermentation media to a concentration of 10.7 [(g alkeneprecursor)/(kg total media)]. The reactive distillation unit waspreheated to >120 [° C.] via pressure control. The media containing thealkene precursor was fed to the reactive distillation unit operationinitially at 275 [g/h] to flush the recovery heat exchanger andestablish media holdup in the reboiler (FIG. 8). The reboilertemperature was increased from approximately 135 [° C.] to a controlledtemperature set point of 149 [° C.] (FIG. 9) and the feed rate wasdecreased to approximately 160 [g/h], allowing the approach to steadystate operation. The double bond concentration in the vapour productfrom the flash drum was analysed continuously for a period ofapproximately 3 [h] (FIG. 8 and FIG. 9), confirming the production ofisobutene to high conversion as anticipated by Example 1. The resultspresented in FIG. 8 and FIG. 9 demonstrate that3-hydroxy-3-methylbutyric acid can be converted in concentrated DSMZ-81fermentation media to isobutene in a reactive distillation unit withsteam contact at elevated temperature and acidic pH.

1-18. (canceled)
 19. A method producing an alkene product comprising:(a) extracting fermentation broth to produce an extracted alkeneprecursor mixture; and (b) implementing a dehydration reaction toproduce from the extracted alkene precursor mixture an alkene productmixture comprising the alkene product.
 20. The method of claim 19,further comprising a polishing distillation step after step (b).
 21. Themethod of claim 19, wherein the extraction step (a) comprises contactingthe fermentation broth with a solvent to extract the at least one alkeneprecursor.
 22. The method of claim 21, wherein the solvent is selectivefor 3-hydroxyacids and secondary alcohols, largely immiscible in waterand supports Mulzer dehydration reactions.
 23. The method of claim 22,wherein the solvent comprises a long chain ester.
 24. The method ofclaim 23, wherein the long chain ester solvent comprises at least one ofhexyl acetate and octanyl acetate.
 25. The method of claim 22, whereinthe 3-hydroxyacid precursor to an alkene product is chosen frommevalonate, 3-methyl-3-hydroxybutyrate, 3-hydroxypent-4-enoate,3-methyl-3-hydroxypent-4-enoate and 4-methyl-3-hydroxypent-4-enoate. 26.The method of claim 22, wherein the alcohol precursor to an alkeneproduct is chosen from 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol,2-methyl-3-buten-2-ol, 3-buten-2-ol and 3-methyl-3-buten-2-ol.
 27. Themethod of claim 19, wherein the alkene product is chosen from isoprene,1,3-butadiene, and isobutene.
 28. The method of claim 19, wherein thedehydration reaction comprises contacting the extracted alkene precursormixture and a Mulzer dehydrating agent.
 29. The method of claim 28,wherein the Mulzer dehydrating agent isdimethyl-formamide-dimethylacetal.
 30. The method of claim 19, furthercomprising separating the alkene product from the alkene productmixture.
 31. The method of claim 30, wherein the alkene product isseparated from the alkene product mixture by at least one of adsorption,membrane separation, and distillation.
 32. The method of claim 31,wherein the alkene product is separated from the alkene product mixtureby adsorption.
 33. The method of claim 32, wherein the alkene product isseparated from the alkene product mixture by adsorption to a zeolite.34. The method of claim 31, wherein the alkene product is separated fromthe alkene product mixture by membrane separation.
 35. The method ofclaim 34, wherein the alkene product is separated from the alkeneproduct mixture using a zeolite membrane.
 36. The method of claim 31,further comprising condensing the alkene product. 37-77. (canceled)